Error Testing Restored Databases
When testing (executing the PowerShell command Test-ContentDatabase) a restored content database in the SharePoint 2013 farm, an error message similar to this may be received:
Database [wss_content_21822_EBS] has reference(s) to a missing feature: Id = [4822d9ca-c6b1-46ab-993a-89a9cfb4e4ac],
Name = [StoragePoint], Description = , Install Location = [StoragePoint].
It is because the externalization was not set to No before performing the content database backup on the SharePoint 2010 farm. It doesnt prevent the database from being mounted or upgraded.
Using 2010 User Interface in SharePoint 2013
It is recommended that all site collections use the SharePoint 2013 user interface after the database attach upgrade. If the SharePoint 2010 user interface is used, some profiles may experience errors when changing externalization from No to Yes.